swift ios使用循环为多个子视图添加约束

Question

我是swift的新手，尝试学习如何使用循环添加几个子视图及其约束。我试着遵循一些类似问题的答案，但它不起作用。你能帮我写代码吗？提前谢谢你。

下面是我的代码：

    let card = UIView()

    let view2 = UIView()

    view2.backgroundColor = UIColor.greenColor()

    view2.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(view2)

    let leftSideConstraint3 = NSLayoutConstraint(item: view2, attribute: .Left, relatedBy: .Equal, toItem: view, attribute: .Left, multiplier: 1, constant: 0.0)
    let topConstraint3 = NSLayoutConstraint(item: view2, attribute: .Top, relatedBy: .Equal, toItem: view, attribute: .Top, multiplier: 1, constant: 0.0)
    let widthConstraint3 = NSLayoutConstraint(item: view2, attribute: .Width, relatedBy: .Equal, toItem: view, attribute: .Width, multiplier: 1, constant: 0.0)
    let heightConstraint3 = NSLayoutConstraint(item: view2, attribute: .Height, relatedBy: .Equal, toItem: view, attribute: .Height, multiplier: 1, constant: 0.0)
    view.addConstraints([leftSideConstraint3, topConstraint3, heightConstraint3, widthConstraint3])



    var cards = [UIView](count: 16, repeatedValue: card) // array with 16 cards



    card.layer.borderWidth = 3
    card.layer.borderColor = UIColor.blackColor().CGColor
    card.backgroundColor = UIColor.orangeColor()



    var columnCounter:Int = 0
    var rowCounter:Int = 0


    //Loop through each card in the array
    for index in 0...cards.count-1 {



        // place the card in the view and turn off translateAutoresizingMask
        let thisCard = cards[index]
        thisCard.translatesAutoresizingMaskIntoConstraints = false
        view2.addSubview(thisCard)

        //set the height and width constraints
        let widthConstraint = NSLayoutConstraint(item: thisCard, attribute: .Width, relatedBy: .Equal, toItem: view2, attribute: .Width, multiplier: 0.25, constant: 0)
        let heightConstraint = NSLayoutConstraint(item: thisCard, attribute: .Height, relatedBy: .Equal, toItem: view2, attribute: .Height, multiplier: 0.25, constant: 0)
        view2.addConstraints([heightConstraint, widthConstraint])

        //set the horizontal  position

        if (columnCounter > 0) {

            // card is not in the first column
            let cardOnTheLeft = cards[index-1]

            let leftSideConstraint = NSLayoutConstraint(item: thisCard, attribute: .Left, relatedBy: .Equal, toItem: cardOnTheLeft, attribute: .Right, multiplier: 1, constant: 0)

            //add constraint to the contentView
            view2.addConstraint(leftSideConstraint)

        } else {

            //card is in the first column

            let leftSideConstraint = NSLayoutConstraint(item: thisCard, attribute: .Left, relatedBy: .Equal, toItem: view2, attribute: .Left, multiplier: 1, constant: 0)

            //add constraint to the contentView
            view2.addConstraint(leftSideConstraint)

        }


        //set the vertical position

        if (rowCounter > 0) {

            // card is not in the first row
            let cardOnTop = cards[index-4]

            let topConstraint = NSLayoutConstraint(item: thisCard, attribute: .Top, relatedBy: .Equal, toItem: cardOnTop, attribute: .Bottom, multiplier: 1, constant: 0)

            // add constraint to the contentView
            view2.addConstraint(topConstraint)

        } else {

            //card is in the first row

            let topConstraint = NSLayoutConstraint(item: thisCard, attribute: .Top, relatedBy: .Equal, toItem: view2, attribute: .Top, multiplier: 1, constant: 0)

            //add constraint to the contentView
            view2.addConstraint(topConstraint)

        }



        //increment the column counter
        columnCounter = columnCounter+1

        //if the column counter reaches the fifth column reset it and increase the row counter
        if (columnCounter >= 4) {
            columnCounter = 0
            rowCounter = rowCounter+1
        }




    } // end of the loop

Answer 1

这将创建一个具有16个对同一张卡的引用的数组。

var cards = [UIView](count: 16, repeatedValue: card)

将其替换为：

var cards = (1...16).map { _ in UIView() }

这将导致具有16个唯一UIView的阵列。